


A Strange Friendship

by Nerdytrashcan



Category: Undertale
Genre: Abuse, BDSM, Belittlement, Dehumanization, Dungeon, Fontcest, Food Deprivation, Kidnapping, M/M, Objectification, Rape, Sadism, Sanscest - Freeform, Stockholm Syndrome, Swapfell
Language: English
Status: In-Progress
Published: 2017-04-09
Updated: 2017-04-10
Packaged: 2018-10-16 18:43:03
Rating: Explicit
Warnings: Graphic Depictions Of Violence, Rape/Non-Con
Chapters: 2
Words: 1,993
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/10577235
Author URL: https://archiveofourown.org/users/Nerdytrashcan/pseuds/Nerdytrashcan
Summary: Sans is having relationship troubles at home, but all of this changes when a certain edgy skeleton kidnaps him.





	1. Chapter 1

**Author's Note:**

> If you want to help me out, consider re-blogging or liking on my tumblr, it really helps me out. Constructive criticism is always welcome. Enjoy! - Nerdytrashcan
> 
> https://nerdytrashcanfanfiction.tumblr.com/post/159370289153/a-strange-friendship-a-fontcestsanscest-lemon

“Eggs, sugar, bread, milk, ketchup, flour… Anything else?” Sans uttered into the phone. “Uh… Yes please. Could you pick up some butterscotch..?” A female voice responded. “Uh, yeah sure. See ya’ tori… Love ya’…” Sans finished, clicking the phone off. Toriel and Sans were in a bit of an awkward place. They loved each other dearly, but once every few months, they had issues… Sexually. Non-biological monsters are hermaphrodites, even if they generally adapt socially to a biological sex. This is fine for the most part, but leads to mating problems when with a biological monster. Sans had gone into a female heat a few days ago, and skeleton heats last a week and a bit generally and last for longer if they don’t mate. Sans’ biggest embarrassment was knowing he had more dildos than his wife. He had to relieve himself often to satisfy his heat, but this was difficult with Frisk and Asriel around. He was well and truly, ‘boned’. The pun Sans made in his head made him chuckle, but it didn’t solve his problem. Sans was deep in thought when he felt his shopping cart hit another, he was about to apologize when he heard extremely loud screaming with a surprisingly high pitched voice. “YOU MOTHERFUCKING PEASANT, I’LL CUT YOUR DICK OFF AND SHOVE IT UP YOUR ASS!” Sans didn’t even need to look up to know who it was. “Hey Swapfell.” Sans responded. “Oh. It’s you. Ugh.” The voice responded. Sans eventually looked up. A small skeleton wearing red and black armor with red star eyes. Whenever Swapfell gets pissed, unless you want 3 sharp bones through your soul, you better help Swapfell with exactly what he wants. “YOU BETTER FUCKING HELP ME WITH THIS SHIT, YOU NEARLY KNOCKED MY PHONE OUT OF MY FUCKING HANDS!” Swapfell yelled again. “Yup… What do you want me to do?” Sans conceded. “Help me with my fucking groceries!” Swapfell shouted once more, lowering his voice slightly. Sans let out a deep sigh. Not wanting particularly to die painfully, he gave up and agreed to help Swapfell. He found a corner to leave his shopping cart and left the supermarket. Swapfell naturally had the edgiest car of all time. A red and black four-wheel drive covered in spikes and exhaust pipes the size of the skeleton the drives the amalgamation. Naturally, Sans was hauling the entire cart. “I want the entire thing done neatly, any mistake will cost you a finger whelp!” Swapfell shouted for the eighth time today. “Uh huh.” Sans replied, opening the boot. The boot popped open with a click and Sans picked up a grocery bag. Sans was proceeding to put the bag into the trunk when he felt a sharp pain in his middle vertebrae. Magic was already seeping to the wound but was beginning to fail. Sans knew he shouldn’t have trusted Swapfell, but Sans had to admit, he didn’t expect this. Sans didn’t know much about chemistry, only quantum physics, but you didn’t need to know much to figure out he was tranquilized. It would only be a few moments before he would be knocked out. His magic was too preoccupied with the wound to summon bones or blasters nor could he teleport and Sans couldn’t run far in his state, so Sans had to play along for now. He felt himself be picked up and shoved into the boot and heard the lock click shut. The drug was really starting to take effect now. It had nearly fully knocked him out and suppressed most of his magic. Sans had 2 choices, struggle or rest. Sans knew he should fight the drug… But sleeping seemed so good to him right now. Sans’ eye-lights dimmed as he felt his skull’s eye sockets shut. He cursed under his breath as he fell victim to the chemicals. Sans woke up with a throbbing headache. He had never had one this bad in a long time. Did he drink, not that he can remember. Did he hurt himself, if he did he would have just dusted, so what could it be? Sans tried desperately to remember, and then shot into action once he did. Bone attacks failed, blasters wouldn’t fire and teleporting didn’t do shit. Sans tried not to panic and began to scan the area. It was black, very much so. He could make out a small red dot light but not much else. He felt himself for anything out of the ordinary, he was chained to something. He also noticed that he didn’t have much in the way of clothes, just his jacket with no shirt underneath, nothing in his pockets either. He smelt a faint stench of old condiments, not ketchup… But barbecue sauce? Not a common choice. He could hear a faint panting if he listened hard enough, along with a chewing sound. Sans reflexes struggled knowing he was not alone. “Who are you?” Sans shouted, trying to stay calm. The panting got louder. What was he alone with. A monster? A Human? Was it also prisoner? Was it chained up? What was that chewing sound? All of these thoughts rushed through Sans’ head until he heard a door creak open. Light flared into the room as Sans tilted his head towards the sound. It was to his left and up, at the top of what appeared to be a staircase, so logically he was in a basement. He used the brief light to look at the source of the panting. The light was faint but he could see a skeleton on all fours, not unlike Sans’ brother, Papyrus. Long and lanky. The skeleton did have it’s share of differences. It was covered in cracks and was chipped in several places, one of his left ribs was missing all together. To top it all off, the skeleton had one tooth missing, and in its place was a shining golden replacement. Still drowsy, it took Sans a few moments to figure out that this was Swapfell’s brother. Sans had been told by Swapfell himself once that his brother was dusted, but the skeleton that lay in his wake told a different story, one Sans was sure he didn’t want to know. 


	2. Chapter 2

**Summary for the Chapter:**

> Sin... Lots of it.

Fear. Raw, primal, fear. People scarcely can comprehend this level of emotion. Sans finally knew what this felt like. Sans' senses were heightened. He could feel the air move around him, he could feel his soul beating in his chest. The broken thing in front of him looked up and the source of the sound, his menacing look turning into one of glee. Sans decided to check the source as well. At the top of the staircase, stood Swapfell, holding a strange handle with many ropes hanging off of the tip, and a ring of keys similar to one that a jail warden would hold. He was grinning a sadistic smile as he proceeded to start walking down the stairs. He had a feminine sway in his step, extremely sexual-like. He was wearing his guard armour, so his extremely high heels clicked and clacked against the wooden staircase, leading onto the dilapidated brick prison. Sans knew Swapfell had something planned, and chances are it involved the broken pile of animated bones across the room. “Comfortable are we?” snickered Swapfell, looking towards Sans. The other skeleton looked towards Swapfell and started to speak, sheer glee in it's voice. “My lord..!” the skeleton started, “SHUT IT MUTT!” Swapfell screamed back before the other skeleton could finish. This put Sans in a higher level of fear, which Sans could not believe was even possible. “I apologise for the interruption. My pet is quite needy.” Swapfell taunting the other skeleton. Sans could not believe the maniac skeleton's treatment of his taller brother. “Now Sans, you are here as our guest. I will be accommodating you until we have both achieved our goals.” Swapfell spoke with a sneer in his voice. “Wh-wh-what the stars are you talking about?” Sans responded, his confidence shattering. “Oh, I think you know. You reek of lust.” Swapfell sensually muttered. Sans eye-lighs went out and his left eye flared to life, the whole room lighting up, flashing yellow and light-blue. Sans' attempt to overdrive his magic were left in vain, as when he attempted to conjure a blaster, his soul let out a sharp pain. “ARRGH! What did you do to me..?” Sans screamed through his tears. “Just a bit of restriction. It would pay you well to listen to me.” Swapfell scowled menacingly, enjoying the torture Sans was experiencing. “The reason your magic is failing is due to your heat.” This caused more questioned to rush through Sans' head, how did Swapfell know about his heat? “It isn't hard to tell, the blue glow in your shorts when you were talking to Toriel. Sans' mind was completely shot at this point, his magic overload fried his sense of comprehension, and knowing Swapfell had been aware of Sans' life, caused his mind to break. Swapfell intended to exploit this fully. “You will listen to me, my dog is having issues with heat as well. He needs to mate, and I don't have the time. You will be his bitch until I finish my latest assignment.” Swapfell cooed. Sans would fight back, but he was too tired and too broken to do so. “Mutt.” Swapfell shouted, jolting his head towards the other skeleton. “My lord!” The 'mutt' responded. “I will release you from the chain. You move towards me, I dust you.” this caused the larger skeleton's large grin to turn to a frown. “Please my lord... I want to fuck you... Please.” The skeleton begged. “Shut it. You get what you're given.” Swapfell barked back, causing the other skeleton to jump in surprise. Swapfell began to walk over to the chain restricting the lanky skeleton. As soon as the lock was released, the skeleton pounced onto Swapfell, conjured his magic immediately and started to dry hump him. Swapfell's body had conjured it's own magic, visible through it's clothes, but Swapfell was having none of it. “YOU FUCKING PRICK!” Swapfell yelled as he grabbed the cat o' nine tails and flogged the other skeleton over the face with it. The tall skeleton finally released Swapfell from it's grasp after 7 consecutive whips to the face. Sans looked on in horror. He could not believe that 'this' was a healthy relationship, where both were happy. He could not believe that Swapfell was so sadistic, even the Classic Fell were not this evil. Swapfell's brother was whining in the corner, making sounds just like a sad puppy. “IF YOU FUCKING TRY THAT AGAIN, I'M NOT FEEDING YOU FOR A MONTH! DON'T EXPECT DINNER TONIGHT EITHER YOU FUCKING DOG!” Swapfell screamed at the taller skeleton, pulling off his belt. As soon as the belt was off, Swapfell folded it in half and used it to slap his brother across the face. He continued this until his brother was sufficiently obedient. “I'm leaving for my shift.” Swapfell yelled as he started to re-ascend the staircase. “Have fun you two.” Swapfell sneered, his head turned towards the dungeon as he clicked the door shut and the lights turned on. This was the first opportunity Sans got to really analyse his surroundings, not that there was much too see. It was a plain grey brick room. He had a cat bed to sleep on and milk in a cat bowl to drink. He was scared. He was sad. He was angry. He was so many things, but above all, he missed his wife. He would do anything right now for Toriel to give Sans a hug, too say everything was ok, that everything was going to work out, that he would see the kids soon. But as the broken pile of bones in front of him leaped at him with magic conjured in his groin, he knew that wasn't going to happen.

 


End file.
